1. Field of the Invention
The present invention relates to a rolled plate-like or plate-shaped body (hereinafter plate-like body refers to plates, sheets or films) pigmented with a converging pigment which comprises a crystalline thermoplastic resin, has a high tensile strength and can be made partially transparent and in which the color of the converging pigment can be seen clearly and brilliantly at the edge portion of a region thereof which is made transparent, while it is opaque at the roughened face side as well. The present invention also relates to a method for preparing such rolled plate-shaped bodies.
2. Description of the Prior Art
Converging pigments have conventionally been used by incorporating them into resins which have high transparency, but are amorphous in nature, such as polycarbonate, polystyrene, poly(methyl methacrylate) and polyvinyl chloride. However, these resins are amorphous and accordinqly, the molded products such as films and sheets produced from the resins do not show high tensile strength. The tensile strength thereof is at highest on the order of 3 to 8 kgf/mm.sup.2. On the other hand, the crystalline thermoplastic resins can provide molded products having a high tensile strength. However, crystalline regions and amorphous regions in general coexist in these crystalline resins although they are, as a rule, called crystalline polymers and correspondingly the densities and the refractive indices of these regions are different from one another. More specifically, they have a multimolecular structure from the optical viewpoint and, therefore, a large quantity of light is scattered within the sheet or film and thus the converging pigment cannot sufficiently show its effect. Since there has not yet been developed any means for solving the problem, it is difficult to uniformly incorporate any converging pigment into the crystalline thermoplastic resins.
Under such circumstances, the inventors of this invention have already found out that if a sheet or a film of a crystalline thermoplastic resin is subjected to a rolling treatment, the tensile strength of the crystalline themoplastic resins can be substantially improved, further the crystal grains present therein are broken and as a result, the quantity of light diffused within the sheets of the crystalline thermoplastic resin can be reduced (in other words, the transparency of the sheet can be enhanced) and that under such a condition, a converging pigment can show its function sufficiently even in the crystalline thermoplastic resins. This technique was already disclosed in Japanese Patent Application laid-open No. Hei 2-167723.
However, there has sometimes been desired, depending on the applications, a plate-like body which is as a whole opaque and whose any desired portion can be locally made transparent according to need and which makes it possible to clearly and brilliantly observe the color of a converging pigment through the edge of the transparent portion.